I am running a 3D VOF simulation of a Lead-Acid battery using Fluent (300,000 cells). We want to simulate the rotation phenomena of a fluid in a box. Rtoating the box, when the flow reaches to fine complex geometry, it is required to reduce the time step (i.e. 10e-8). From an engineering point of view, this time step is not acceptable. It would be highly appreciated if you send me any comments regarding my problem.